In aging mice, bone marrow fat cells secrete DPP4 and other factors that activate the cGAS–STING pathway in marrow macrophages, producing chronic inflammatory signaling that suppresses bone formation and lowers NAD⁺ in osteoblast progenitors. Silencing STING specifically in macrophages between 12 and 18 months preserved bone density and architecture, increased new bone deposition, and reduced marrow fat accumulation. The work positions innate immune sensing of displaced DNA as an upstream driver of age-related skeletal decline rather than a bystander.
Key Points
- cGAS–STING activation rises progressively in marrow macrophages with age
- Macrophage STING silencing preserved bone density and reduced marrow fat
- Fat-cell DPP4 and circulating endotoxin amplify STING-driven inflammation
Longevity Analysis
Bone loss here is not primarily a calcium or mechanical-loading problem but an immune signaling problem, with marrow fat acting as an endocrine source of inflammatory input and macrophages translating that input into suppressed osteoblast function. The involvement of gut-derived endotoxin and leaked mitochondrial DNA as upstream triggers links barrier integrity and mitochondrial quality to skeletal maintenance, which means reducing inflammatory load upstream may matter as much as any bone-directed agent. The accompanying NAD⁺ decline in bone-forming cells connects cellular energy capacity directly to the tissue's capacity to rebuild itself.
Original published by LifeSpan.io, by Arkadi Mazin.